Standby or demand or inhibited or synchronized type cardiac pacemakers are provided with means to convert the standby or sensing state to a fixed predeterminated pacing rate mode which allows several tests of the pacer to be performed, and of its system, such as tests of the cell or battery voltage, which is indicated by the deviation in the testing rate or/and stimulating spike width; the stimulation threshold; the electrode system malfunctions; and other parameteric measurements. This fixed predetermine testing rate induces competition between the cardiac spontaneous rhythm and the pacer stimulating rate.
This competition may develop a spike-on-T phenomenon, this latter being known as a cardiac vulnerable period, and this may be dangerous in case of active coronary insufficiency. The object of this invention is to reduce this danger by introducing synchronization of the fixed testing rate with the spontaneous cardiac rhythm.
Additionally, there is a need for heart stimulation in order to terminate tachyarrhythmias by reverting to normal sinus rhythm. Today this is done by stimulating the heart with high frequency electrical spikes until the desired conversion occurs. Application of the hereby disclosed synchronization system carries the stimulation spike into the diastole period, thus, terminating the tachyarrhythmias more efficiently and without the danger of overstimulation.
According to a further feature of the present invention, means are provided for terminating tachyarrhythmias, in patients with implanted demand or other pacemakers, and this is accomplished by means of application of heart stimulation at a predetermined higher frequency. According to a preferred embodiment, means are provided for applying a stimulating spike for terminating such cardiac tachyarrhythmias, said spike being applied into the diastolic period, and means for repeating such stimulating spikes, as required, synchronized with the heart beat rate, and for repeating such stimulation at predetermined intervals.
The novel device is based on conventional circuitry, and preferable on C-MOS technology logic circuits which exert a low current drain on the energy source. Linear circuit means can also be used for such devices.